ANALYSIS OF HLA-DQ-ALPHA SEQUENCES FOR PRENATAL-DIAGNOSIS IN SINGLE FETAL CELLS FROM MATERNAL BROOD

We have extended a previously developed method that allows prenatal DN A diagnosis of female fetuses through the isolation of single nucleate d erythrocytes from maternal blood by developing a method that can dis tinguish between maternal and fetal nucleated erythrocytes. Nucleated erythrocytes were separated by a density-gradient method and then coll ected by micromanipulation. Sex was determined after primer extension preamplification (PEP) of the entire genome of a single cell, and huma n leukocyte antigen (HLA)-DQ alpha type was determined after further a mplification of this gene. The HLA-DQ alpha genotype of fetal erythroc ytes in maternal blood samples and their corresponding paternal and ma ternal lymphocytes were successfully determined in all cases. The accu racy of the method was determined by using single nucleated erythrocyt es from umbilical cord blood from five normal deliveries. This is the first demonstration that the fetal HLA-DQ alpha gene sequences can be identified in a small aliquot of a single nucleated erythrocyte in mat ernal blood. We believe that this method ushers in a new era in which the reliability and accuracy of noninvasive prenatal DNA diagnosis fro m maternal blood is markedly improved.